Electric induction apparatus



P l95! A. MITE'ERMAIER 2,521,533

ELECTRIC INDUCTION APPARATUS Filed March 15, 1948 Fig. I.

Fig.2.

Fig. 5.

Inventor: Armin EMiLLeYma'i er,

by His Abborney.

Patented Sept. 5, 1950 UNITED ELECTRIC INDUCTION APPARATUS Armin F. Mittermaier, Fort Wayne, Ind., assignor to General Electric Company, a corporation of New York Application March 13, 1948, Serial No. 14,752

3 Claims. 1 This invention relates to electrical induction apparatus which has a magnetic core constructed of sections made up of stacked punched laminations and more particularly to a clamping means for such a core structure.

In electric induction apparatus having a magnetic core made up of sections which are constructed of stacked punched laminations it is necessary that some clamping means be used to bind the laminations closely together and force the core sections into proximity to one another. Aside from the physical consideration of the rigidity of the core structure, the clamping means should be such as to decrease the noise and to minimize the losses which are normally present in apparatus of this type.

It is anobject of this invention to provide a new and improved clamping arrangement for electric induction apparatus having a laminated magnetic core structure which is both efiicient and economical.

Another object of this invention is to provide such a clamping arrangement which allows for the automatic assembling of the core structure and clamping mechanism.

It is a further object of this invention to provide such a clamping means whose installation requires the removal of no magnetic material from the core and does not require the use of nuts and bolts or springs.

Still another object of this invention is to provide a new and simple clamp which may be utilized to hold together a laminated core structure. this function being effected by means of welding.

This invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 is a front elevation, before final assembly, of a particular embodiment of this invention used with the laminated core structure of a two-lamp fluorescent ballast showing the ballast coils in section.

Fig. 2 is a plan view of the two-lamp fluorescent ballast before final assembly showing the ballast coils in section.

Fig. 3 is a front elevation of the completely assembled two-lamp fluorescent ballast.

Referring now to the drawing there is shown in Fig. 1 by way of example a two-lamp fluorescent ballast I which is used for supplying operating voltages to gaseous discharge lamps, or fluorescent lamps, and for limiting the current magnitude in the fluorescent lamp circuit. The fluorescent lamp ballast I supplies the increased 2 operating voltage to the lamp circuit by mean of an autotransformer 2 which is constructed of a coil 8 wound on the central leg of a magnetic core 4 which is made up of alternately stacked punched E and I-shaped laminations. The circuit current is limited by the reactors 5 and G which have coils 1 and 8 wound on the central leg of stacked E-shaped laminations 9 and III. The reactors 5 and 6 abut the central autotransformer 2 and are normally separated from it by small air gaps II nd I2.

The autotransformer 2 is clamped together as a unit by the use of the clamping wedges I3 which may be formed from lamination steel and have a modified W-shape as shown in Fig. 1. The

' core 4 is stacked between the wedges I3 so that the middle crest of the W presses against the inner side of the coil 3 and the two outer or lower points of the W'force the stacked E and I-shaped laminations 4 together. The E-shaped reactors 5 and 6 are held together by the use of E-shapecl clamping pieces I4, the central leg of which is very similar to the clamping wedge I3. The E-shaped laminations 9 and III are stacked between the clamping pieces I4. The main body of the E-shaped clamping pieces I4 is ridged at I5 so that the compressive force is evenly distributed over the whole length of the E laminations 9 and III. The reactors 5 and 8 are then forced into abutting position against the autotransformer as shown in Fig. 3. The outer legs of the E-shaped clamping pieces I4 are long enough so that they overlap the central autotransformer core 4 and after the air gaps II and II have been adjusted to the proper width the outer legs of the E-shaped clamping pieces I4 are welded at I6 as shown in Fig. 3 to the upper and lower surfaces of the E-shaped laminations of the autotransformer core 4. Therefore, not only are the laminations of the fluorescent ballast I forced tightly together but also the core sections (1. e. the autotransformer 2 and the two reactors, 5 and 6) are held firmly as a unit. In order to prevent any relative movement of the laminations oi the fluorescent ballast I the air gaps II and I2 may be filled with a cement.

While there has been shown and described a particular embodiment of this invention it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent oi the United States is:

1. Electric induction apparatus comprising, in combination, at least two magnetic cores composed of stacked laminations, a conductive winding linking each core, sheet metal pieces each having a resilient deformed portion wedged between each winding and its core for clamping the core laminations tightly together, the metal pieces for clamping one of the cores having extensions which overlie the other core, and means for attaching said extensions to said other core for holding said cores together as a unit.

2. A ballast for two discharge lamps comprising, in combination, an auto transformer having a core of interleaved E and I-shaped magnetic punchings with a conductive coil on the center leg of the core, bent sheet metal clamping strips wedged between said core and coil for clamping the core laminations together as a unit, two reactors each comprising a core of stacked E-shaped magnetic punchings with a coil on the center leg of the E-shaped stack, E-shaped sheet metal clamping members having bent center legs wedged between the reactor coils and their cores for clamping the laminations of the reactor cores together as a unit, the legs of the reactor cores and the legs of the clamping members running in the same direction, the outer legs of the reactor clamping members being extended so as to overlap and embrace the outer E-shaped laminations of the autotransformer core, and welds for at- OJBIJSS 25 Number tacbinflthe extended ends of the outer legs of the reactor clamping members to the outer E- shaped laminations of said autotransiormer core so as to hold said three cores together as a unit with predetermined gaps between them.

3. A combined core clamp and mounting bracket for electric induction apparatus comprising a unitary generally E-shaped sheet metal stamp n the center leg oi the E being substantially shorter than the two other legs, the center leg being curved so as to act as a clamping wedge between a core and coil, the ends of the outer legs serving as mounting feet, the cross member of the E being stifiened by having its outer edge extending at an angle to the remainder thereof so as to transmit core clamping pressure throughout the width of said stamping.

ARMIN I". MITIERMAIER.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Name Date Dubilier Jan. 15, 1924 Frank July 1, 1930 Mittermaier May 18, 1943 Zelt Sept. 26, 1944 Kronmiller Aug. 12, 1947 Galla Dec. 2, 1947 Mittermaier Jan. 10, 1950 

